Adolecent Medicine Update: Anorexia Nervosa

For many practitioners, teenagers with eating disorders elicit a visceral reaction. Many clinicians find it difficult to imagine why an adolescent might choose to starve herself or even make herself vomit. Understandably, they become increasingly frustrated with the emaciated- appearing patient who insists that she is "too fat" and "needs" to lose 10 more pounds. Anorexic teenagers tend to take a great deal of the physician's time and usually demonstrate few (if any) appreciable short-term improvements. The knee-jerk reaction may be to immediately refer these "frustrating" patients to a local academic center's adolescent medicine specialist. While consultation with a specialist may be appropriate, the primary care physician still plays a fundamental role in the initial diagnostic workup and in long-term management.

Here I review some of the information that a primary care physician needs to remember when evaluating a patient who may have anorexia nervosa (AN). Rather than attempting to offer a comprehensive review, I present a basic framework for understanding malnutrition. I also focus on clinical clues, physical examination findings, and laboratory tests that help streamline referral to a tertiary care eating disorder specialist.

Kristen, 16, is an all-around "good kid." You have known her and her family since she was a preschooler. Aside from the occasional "strep" throat or flu, she has been in excellent health. She comes to your office today for her annual sports physical examination. Kristen is a junior varsity long-distance runner; she hopes to make the varsity team next year. She played the leading role in her high school musical this year and has made the honor roll every semester.

Kristen has no physical complaints. She denies any alcohol(, cigarette, or drug use and says she has never engaged in any sexual activity.

A look at Kristen's growth chart reveals that her weight has dropped from 125 to 108 lb since you last saw her. An eating disorder comes to mind.

What do you do now? What will you say or ask?

Termed "nervous consumption" in the 19th century, AN is characterized by a dramatic weight decrease accompanied by an obsession with nutritional intake. The disease affects as many as 1 in 200 white adolescent girls; the mean age at onset is between 13 and 14 years. The risk of AN is 10-fold higher in girls than in boys.

The diagnostic criteria for AN as defined in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR)¹ are outlined in the Table. In brief, patients with AN have a disturbed perception of their body shape that is accompanied by an intense fear of gaining weight. They become obsessed with their weight and caloric intake such that they cannot rationally interpret their situation.

Patients are classified (by subtype) according to the methods used to lose weight:

•In the "restricting" subtype, patients either severely limit their caloric intake or exercise excessively to burn off calories.

•In the "binge-eating/purge" subtype, the adolescent engages in binge-eating episodes followed by purging through laxative use or self-induced vomiting.

Patients with either subtype maintain and amplify their weight loss to the point at which symptoms and signs of malnutrition develop. Associated morbidity and mortality correlate with the degree of malnutrition.

Typically, weight loss troubles the patient's friends and family--not the patient. Most adolescents with AN present for medical care because their family and friends are concerned about their dramatic weight loss and its biologic effects.

The diagnosis and treatment of AN frequently involves a multidisciplinary team that includes an eating disorder specialist, a psychotherapist, a nutritionist, and the primary care physician. While the primary care physician may not have time and/or expertise to perform a comprehensive evaluation, he or she can play a vital role in manag-ing the nutritional sequelae of the patient's disease.

You ask Kristen about her weight loss. She knows she has lost a "little" weight but attributes this to the attention she is giving to her diet as well as her running. Kristen says she eats "well" and has no concerns about her weight. She denies any purging behaviors and insists: "Believe me, I'm not bulimic or anything like that! That's gross."

On hearing this, Kristen's mother--who has been present during the history taking-- interrupts and asks to speak with you alone. You both go to a consultation room where her mother says: "Kristen is lying to you, just like she lies to everyone these days. She has been dieting since last year when a boy made a mean comment about her being a little overweight. At first she just cut out the junk food and she started to look really healthy. Lots of people told her how good she looked, which in- creased her desire to lose even more weight. Over the past few weeks, her dieting has really gotten out of control. I spent the entire day with her last Saturday and she ate 1 piece of toast for breakfast, a small salad (with no dressing) for lunch, and a half a bagel for dinner. That was it! On top of that, I found out that she is doing 800 to 1000 sit-ups a day on top of her track exercises. Don't you think she is overdoing it?"

Does Kristen have an eating disorder? In retrospect she may, after all, fit the eating disorder stereotype--an adolescent white female from an upper-middle-class family who excels at school, sports, and social activities. You recall that AN begins as an innocent diet inspired by comments made by friends, coaches, or parents. As the initial weight loss elicits positive feedback from peers, the simple diet transforms itself into an obsession with thinness and food intake.

Kristen vehemently denies any obsessional thoughts about food and intake. However, further questioning reveals that she religiously limits her caloric intake to 1000 calories a day! She blames her decreased intake on a lack of appetite. Kristen admits that she frequently feels fatigued and often feels depressed. She also reports that she has problems with constipation, although she has never needed or taken laxatives. Kristen occasionally experiences heartburn. She never faints or has palpitations but occasionally becomes dizzy when standing. Her last menstrual period was 3 months ago.

Consider a broad differential before you diagnose AN in an adolescent who presents with weight loss and malnutrition. As with most diseases, the clinical history provides important clues to ruling out (or in) other processes. For example, inflammatory bowel disease frequently presents with weight loss, but it is often accompanied by bloody stools, diarrhea, abdominal cramps and, occasionally, findings such as joint inflammation and mouth sores. Other inflammatory processes such as systemic lupus erythematosus and juvenile rheumatoid arthritis may manifest with fatigue, fevers, joint pains, weight loss, and rashes. Such complaints should prompt an investigation to rule out these processes. Consider infectious disease, such as HIV, tuberculosis, and intestinal parasitosis, when the history reveals any associated risk factors.

Consider an endocrine abnormality, such as undiagnosed diabetes mellitus, if the patient describes persistent thirst and urination accompanying her weight loss. Hyperthyroidism frequently can lead to weight loss, despite increased food intake; this disorder is generally accompanied by heat intolerance, palpitations, nervousness, sweating, and increased stool frequency. Hypothyroidism can also mimic the failure to thrive seen in AN.

Be sure to assess the adolescent's social environment to determine whether there are any correlating factors that are contributing to the weight loss. For example, teenagers who are homeless, impoverished (and unable to access food), or extremely depressed, or who are abusing illicit substances are frequently malnourished. These underlying factors must be addressed appropriately.

Kristen's physical examination reveals a thin, malnourished- appearing girl who makes poor eye contact and who is occasionally teary. She is 67 inches tall and weighs 108 lb. Her BMI is 16.9 (4th percentile for age). Vital signs: temperature 35.9°C (96.7°F); blood pressure, 110/78 mm Hg; pulse, 61 beats per minute; respiratory rate, 16 breaths per minute. HEENT evaluation is unremarkable. There is fine hair growth (similar to that seen on a baby) on Kristen's arms and legs. The skin is dry and looks slightly yellow. Results of the cardiac evaluation are unremarkable. Her abdomen is noticeably thin. Her hands and feet are cold and her distal digits appear purple.

General pediatricians rarely see patients with severe malnutrition. Thus, the clinician's mental picture of malnutrition may reflect images from underdeveloped areas where children present with kwashiorkor or marasmus. In this country, most adolescents who present with moderate or severe malnutrition demonstrate more subtle physical findings. The most striking initial finding frequently involves muscle and adipose wasting, which accentuates the bony structures (as when Kristen's mother bemoans "She looks like a skeleton!").

When I discuss the effects of malnutrition with my patients, I frequently liken the condition to hibernation. Hibernation sustains animals during seasons in which food will be scarce. Their metabolism essentially slows down so that only the fewest calories necessary to maintain life are burned. Human metabolism undergoes a similar transformation when challenged by a dramatic caloric decrease. This "metabolic hibernation" explains many of the physical findings seen in a malnourished patient with AN.

For example, in a severely malnourished patient, core body temperature is decreased--often to less than 36.1°C (97°F). Heart rate may also be decreased (fewer than 60 beats per minute) and relative hypotension may be present. Using the hibernation analogy, this should make sense because the body is not going to waste extraneous calories to maintain a normal heart rate, blood pressure, or body temperature if caloric intake is unavailable to maintain these functions.

Other stigmata of malnutrition can include lanugo hair on the extremities; yellow-orange discoloration of the hands and feet (caused by carotenemia); and brittle, ridged nails. The distal extremities may appear purple and feel cold to the touch as peripheral blood vessels constrict in an attempt to preserve body heat and caloric energy. Pitting edema of the extremities often occurs as a by-product of severe protein malnutrition. Also, a flat affect and some degree of neurocognitive impairment are frequently present in the anorexic, malnourished patient.

The diagnosis of AN is primarily clinical based on the history and physical examination results. There is no diagnostic laboratory test. However, when you suspect this diagnosis, some basic laboratory evaluations are needed to:

•Rule out other diagnoses.

•Determine the extent of the malnutrition.

•Assess immediate and long-term morbidity risks.

•Help determine what interventions are needed at the time of diagnosis.

A basic electrolyte panel will reveal any significant electrolyte imbalances that exist secondary to the decreased food and energy intake. Patients with the purging subtype of AN often have elevated bicarbonate levels from loss of hydrogen ions through vomiting. Hyponatremia may be present if the patient consumes excess water to artificially augment her weight for the doctor visit. This suspicion can be confirmed by a urinalysis. An elevated BUN to creatinine ratio may also suggest the extent of dehydration present in the event of severe intake restrictions.

A complete blood cell count and erythrocyte sedimentation rate (ESR) screening generally do not contribute much to the diagnosis and management of AN. However, a significantly elevated white blood cell count or ESR might suggest an infectious or inflammatory cause of malnutrition rather than a psychiatric cause. Measurement of prothrombin and partial thromboplastin times is not routinely indicated; however, these tests should be ordered if the patient shows evidence of bruising.

Liver function tests frequently reveal a mild transaminitis during severe malnutrition, which tends to self-resolve as the patient's nutritional status improves. The serum albumin level is frequently decreased, especially if the patient presents with distal extremity edema.

Other investigations, such as an examination for stool ova and parasites or fecal fat, an upper GI series, or an anti-endomysial antibody test (for Celiac disease) may be useful if the history suggests a primary pathologic process. However, if you are certain that the diagnosis is AN, such investigations are unnecessary.

Levels of thyroid-stimulating hormone and T₄ are usually normal in patients with AN. Hyperthyroidism can often be suggested by the history and physical examination. Measurement of T₃ (the bioactive conversion of T₄) can be useful in that levels typically reflect long-term (2- to 4-month) nutritional status. Because the thyroid gland controls metabolism, it makes sense (using the hibernation analogy) that during times of long-standing caloric deficiency this conversion would subsequently decrease. At our facility, we often use a markedly decreased T₃ to help demonstrate the severity of the patient's malnutrition to themselves and their families.

Severe, long-standing malnutrition frequently leads to decreased bone mineral density--regardless of whether the patient is amenorrheic. Because adolescence is a time of maximal bone mineral deposition, the net losses of bone minerals sustained during severe malnutrition often place the patient at a lifelong risk for pathologic stress fractures from osteopenia. The absence of menses for more than 6 months increases the risk and intensity of the bone mineral density loss. Therefore, I recommend a dual-energy radiograph absorptiometry (DEXA) bone density scan in any patient who has had amenorrhea for more than 6 months and/or severe malnutrition for over 9 months.

Severely malnourished teenagers may be at risk for fatal arrhythmias secondary to electrolyte imbalances, cardiac muscle wasting, and/or the use of exogenous substances (such as ipecac syrup) to maintain weight loss. Consider ordering an ECG to assess for low-voltage changes and T-wave inversions caused by potential electrolyte imbalances.

Echocardiography is not routinely recommended, but it may demonstrate decreased left ventricular wall thickness and/or mitral valve prolapse. Some data suggest that the decrease in ventricular wall thickness relative to the unchanged mitral valve size contributes to this finding, but this is controversial.

Typically, girls with moderate to severe malnutrition will stop menstruating as their malnutrition progresses. This is most likely a function of decreasing levels of gonadotropin-releasing hormone secreted by the hypothalamus. With the hibernation analogy in mind, one could speculate that amenorrhea is the body's defense against a potential pregnancy. After all, if the body cannot find enough calories to sustain its own metabolism, it surely will be unable to expend calories sufficient to sustain a fetus.

I recommend a urine pregnancy test in any patient who has missed 1 or more periods--regardless of her nutritional status. Follicle-stimulating hormone and luteinizing hormone levels are typically decreased if tested, but many eating disorder specialists forgo these tests if the patient's malnutrition is clearly contributing to the amenorrhea.

Menses generally resume as the patient recovers from anorexia and regains lean body mass. As a rule, menses return when the patient attains the weight at which her periods stopped.

A discussion of the treatments and prognoses for patients with AN extends beyond the scope of this article and will be discussed in a future issue. Suffice it to say that affected patients deserve at least some consultation with a team of eating disorder specialists that includes a physician, a psychologist, and an experienced nutritionist. Also key to the team's success is the primary care doctor, who provides monitoring and continuity of care--a critical role for the patient's long-term success.